The present invention generally relates to cooling systems, and more particularly to a cooling system which is designed so that an electronic device and a cooling module are accommodated within an airtight box and the electronic device is cooled by operating a coolant supplying unit.
Recently, in supercomputers or the like, the electronic devices consume large power in order to realize high-speed operations and the electronic devices are equipped with a high density. Hence, in order to guarantee stable operation of the electronic devices, namely semiconductor elements, the electronic devices are cooled by a cooling system. It is desirable that the cooling system cools the electronic devices to a relatively low temperature so as to fully bring out the performances of the electronic devices.
On the other hand, in the case of high-speed elements such as CMOS and HEMT elements which operate at high speeds in a low temperature environment or high-speed elements such as Josephson elements which operate only in a low temperature environment, a coolant such as liquid nitrogen and liquid helium is used to cool the high-speed elements.
Accordingly, in the cooling system which cools the electronic device to the low temperature, dew condensation in liquid form or solid form (ice) easily occurs. Hence, it is important that measures are taken to prevent such dew condensation.
FIG. 1 shows an example of a conventional cooling system. The cooling system includes an airtight box 3, a coolant supply unit 4, a unit 8 or 9, and a heater unit 15. An electronic device 1 is equipped with semiconductor elements, and a cooling module 2 cools the semiconductor elements of the electronic device. The electronic device 1 and the cooling module 2 are accommodated within the airtight box 3 which is made of a heat insulating material. The unit 8 absorbs the moisture within a chamber 3A inside the airtight box 3 to prevent dew condensation. The unit 9 replaces the air or predetermined gas inside the chamber 3A by a predetermined gas to prevent dew condensation when the temperature of the coolant is extremely low. One of the units 8 and 9 is provided depending on the needs. The heater unit 15 is used to raise the temperature within the chamber 3A if needed. A door 3B is provided on the airtight box 3, and the maintenance or removal of the electronic device 1 and/or the cooling module 2 can be made by opening the door 3B.
The coolant supply unit 4 supplies a low temperature coolant 5 to the cooling module 2 within the airtight box 3 via a pipe 21 which is covered by a heat insulating material. The coolant 5 is then returned from the cooling module 2 to the coolant supply unit 4 via a pipe 21. Hence, the coolant 5 is recirculated between the coolant supply unit 4 and the cooling module 2. For example, liquid helium, liquid nitrogen, flon, fluorocarbon or the like may be used as the coolant 5.
The coolant supply unit 4 includes a refrigerator 4B which refrigerates the coolant 5 via a heat exchanger 4A, and a pump 4C for forcibly pumping out the coolant 5 towards the airtight box 3. The pump 4C is driven to recirculate the coolant 5 with respect to the cooling module 2.
Accordingly, the unit 8 absorbs the moisture within the chamber 3A or the unit 9 replaces the air within the chamber 3A by a predetermined gas when starting to cool the electronic device 1, and the heater unit 15 raises the temperature within the chamber 3A to a temperature approximately equal to that outside the chamber 3A when stopping to cool the electronic device 1 so as to attend to the maintenance of the electronic device 1 via the door 3B. As a result, it is possible to prevent the dew condensation in liquid or solid form from occurring when starting and stopping the cooling operation.
The cooling system of the type described above is proposed in a Japanese Laid-Open patent application No. 1-318295, for example.
However, when preventing the dew condensation by driving the unit 8, the coolant supply unit 4 may be operated when the humidity absorption is still insufficient. Similarly, when preventing the dew condensation by driving the unit 9, the coolant supply unit 4 may be operated when the replacement of air by the predetermined gas is not yet completed. In addition, when attending to the maintenance of the electronic device 1, the temperature of the cooled electronic device 1 may greatly differ from the temperature outside the chamber 3A. When the door 3B is opened in such cases, there is a problem in that the dew condensation in liquid or solid form occurs, thereby causing corrosion which deteriorates the performance of the electronic device 1.
Accordingly, in the conventional cooling system, the dew condensation in the form of liquid or solid cannot be prevented unless the cooling operation is started depending on the operating states of the unit 8 or 9 and the electronic device 1 and unless the maintenance of the electronic device 1 is attended to depending on the operating state of the electronic device 1.
In addition, the conventional cooling system also suffers from problems in that the system construction is complex due to the piping and sealing required in connection with the unit 8 or 9 and the heater unit 15 which must be connected to the airtight box 3.
Furthermore, when the heater unit 15 heats the electronic device 1, the heating is made via air or predetermined gas. Hence, a fan must be provided to circulate the heated air or the predetermined gas within the chamber 3A, thereby making the system construction more complex. In addition, because the heating is made via air or predetermined gas, there are problems in that the heating of the electronic device 1 is inefficient and time consuming.